1. Field of the Invention
The present invention relates to solar-energy utilization and, more specifically, to solar-heating systems.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Heating, ventilation, and air conditioning (HVAC) systems account for about one half of the energy used in residential buildings in the United States. Solar HVAC technologies can be used to offset at least a portion of this energy. The U.S. Energy Information Administration (EIA) classifies solar-heating systems into three categories: low-, medium-, and high-temperature systems. Low-temperature systems are usually used to heat swimming pools and for space heating. Medium-temperature systems usually generate hot water for residential and commercial use. High-temperature systems concentrate sunlight using mirrors and/or lenses and are generally used for generating electricity.
A typical household solar-heating system is a low- or medium-temperature system that has a solar collector, with a heat-transfer fluid (e.g., air or water) flowing through the collector to absorb solar-generated heat and transport it to a storage or distribution subsystem (e.g., a hot water tank or heat radiator). The solar collector is usually placed where solar-radiation levels are relatively high, e.g., on the roof of the house. A pump circulates the heat-transfer fluid through the solar collector and storage/distribution subsystem, thereby transporting the heat to the place of its intended use.
An important consideration for the individual consumer is the cost and ease of deployment of the solar-heating system. For example, a relatively expensive solar-heating system has a relatively long pay-back period, which makes it unattractive to the consumer. A solar-heating system that is permanent or difficult to deploy might similarly be unattractive because the consumer might prefer to have it deployed only when needed, e.g., during the winter months, and have it removed when not needed, e.g., during the periods of hot weather.